Hi everyone,

In Excel, you see sometimes people doing this although don't know what
is called:

Say you have names listed in many rows. Some rows might each has
sub-names rows. On the far left, before the row numbers column, you see
TWO buttons at the top; one is 1 button for hiding the sub-nambes row,
2 button for expanding sub-names rows!

What is this operation in Excel called? Where can I read about it?

Thanks,
Mike